This invention relates generally to automatic washing machines and more particularly to automatic washing machines designed for ease of manufacture.
As it is known in the art, an automatic washing machine generally includes a tub assembly disposed within a cabinet. The tub assembly includes a spin tub which is rotatably mounted in a drain tub A drive shaft is vertically disposed through the tub assembly and engages the spin tub for rotation thereof. The drive shaft is rotated by a motor coupled thereto and the rotation of the shaft is controlled by means of a transmission.
As it is also known in the art, automatic clothes washing machines are generally cycled through a sequence of operations in the processing of a wash load. For example, these operations may include a presoaking operation, a washing operation, a rinsing operation, and a spin drying operation.
Various factors are considered in the design of a support structure or suspension system for the washing machine tub assembly. Several of these factors influence the performance of the machine For example, the clothes may be unevenly distributed around the spin tub while it is rotated at relatively high speed during a spin drying operation. This phenomena is referred to as an out-of-balance condition and causes high centrifugal forces on the tub assembly at the circumferential location of the out-of-balance load. The high centrifugal forces in turn cause the tub assembly to pivot or tilt. The washing machine suspension should be designed to counterbalance the high centrifugal forces occurring as a result of a out-of-balance condition so that such forces are not transferred to the floor as vertical forces of large magnitude. Large vertical forces are undesirable since they tend to cause the washing machine to shake and, in aggravated circumstances, to physically move or "walk". Furthermore, in addition to performance considerations, the design of a washing machine suspension system should further take into account the ease with which the washing machine is manufactured.
One type of washing machine suspension is a mid-level pivot and traverse arrangement as described in U.S. Pat. No. 4,174,622 entitled "Automatic Washer Suspension System" The mid-level pivot and traverse suspension includes legs that elevate a support structure to a level approximately mid-way between the washing machine base and the top of the washing machine cabinet. A traversing member is disposed on the support structure and is designed to slide or traverse on such structure. The tub assembly, including the drain tub and spin tub mounted therein, is seated on the traversing member. With this arrangement, the pivoting or tilting forces are reduced by the addition of the extra degree of freedom in the horizontal direction. Lower pivoting forces result in lower reaction forces transferred to the floor, and thus, there is a reduction in the tendency of the washing machine to "walk".
More specifically, attached to and disposed underneath the drain tub are three inclined pads comprised of a relatively low friction material When the tub assembly is disposed over the mid-level support structure, the inclined pads attached to the tub assembly mate with complimentary inclined pads disposed on the traversing member. Thus, the tub assembly is free to pivot about the complimentary inclined mating surfaces; and also, the tub assembly can traverse with the traversing member. With this type of washing machine suspension, the spring forces required to hold the tub assembly upright are relatively small since the tub assembly is supported close to the bottom of the drain tub and thus the pivoting moment is relatively small. Due to the small spring forces required and also the horizontal degree of freedom provided by the traversing member, this suspension arrangement is capable of preventing "walking" with larger out-of-balance loads than a conventional base level, fixed pivot suspension.
However, the improved out-of-balance performance of the mid-level pivot and traverse suspension arrangement is achieved at the penalty of manufacture complexity, time, and cost. The ease with which the washing machine is assembled relates directly to the assembly time and is further related to the cost of the machine
In particular, the assembly of the mid-level pivot and traverse arrangement is accomplished in several steps and thus, is both time consuming and costly. For example, a tub module, including the drain tub, spin tub, and drive shaft may be independently assembled and then positioned over the traversing member. However, once such a tub module is in place, the transmission must be attached to the drive shaft and the motor mounted. Also, a right angle drive member which provides coupling between the motor and the drive shaft is mounted after the tub module is seated on the traversing member. Mounting the motor, transmission, and drive member below the tub module may be awkward and difficult due to limited accessibility through the support legs. Manufacture time is also increased by the assembly of the traversing member due to the large quantity of parts that make up the member. Further, increased service and repair time may also be associated with the mid-level pivot and traverse suspension due to the multi-step disassembly required.